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I needed a 40mm wide hole. The shop didn't have a 40mm bit. Necessity is mother of invention so I invented my own hole maker. Here's how I did it.

Of course I could have bought an adjustable bit for the princely sum of 5000 yen but I only needed two holes. Again, necessity is the mother of invention.

One fine day I was building a foot powered lathe inspired by Don Weber. I couldn't find any cheek block bearings anywhere around south Yokohama so I caved and bought some big sealed roller bearings (similar to but larger than those in rollerblades or skateboard wheels). This presented a new problem: I needed to mount the bearings in wood. So why not drill a hole the same size as the bearings? Because I couldn't find an appropriate bit, that's why. Ah yes, the plot sickens.

So naturally I found my solution where I find all my answers: a dead bicycle; the frame of a bike to be precise.

Danger, warning, achtung! Danger, warning, achtung! Danger, warning, achtung!
Danger, warning, achtung! Danger, warning, achtung! Danger, warning, achtung!

This tool is risky. It has a chance of shooting a sharpened hunk of metal at high velocity in a random direction and hurting someone badly. Please be very careful if you use this!

Danger, warning, achtung! Danger, warning, achtung! Danger, warning, achtung!
Danger, warning, achtung! Danger, warning, achtung! Danger, warning, achtung!

Step 1: Parts and tools

Ingredients:
-One thin-walled steel pipe ~3 inches long x an arbitrary width (mine was from a bike frame)
-a screwdriver bit with a hexagonal butt end (this is really just an adapter to mount the bit in a drill).
-two short machine screws and nuts. I used 1/4 inch screws.
-and the secret ingredient: love.

Tools:
-drill
-drill bit the same size as your two machine screws.
-bench grinder (or a file and patience).
-hack saw
-a big flat screwdriver
-vice
-hammer
-measuring tool (vernier calipers recommended)
-love

<p>I need a spade bit 160mm wide and about 360mm long to bore a hole in ytong aerated concrete. (to install ventilation fan). I was thinking of welding a sharpened metal plate to a rebar stick....</p><p>any suggestions welcome.</p>
You have mad skills! I love bike parts for projects too.
Cheers!
So, is this dangerous ? :)<br><br>Nice instructable, thanks for sharing!<br>
Glad you like it :)<br><br>I think it's dangerous. <br><br>So did my neighbor. <br><br>But I did it anyway.
Good! Without risk takers, we'd have nothing! :)
Nice work. Very clever.

About This Instructable

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Bio: Careers: documentary filmmaker, DOP, engineering student, practical environmentalist, idealist. Loves: bicycles and when weeds grow in the city. I'm from western Canada, Yukon, Japan ... More »
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